CONVERGENCE. I5I 



every manual of comparative anatomy affords testimony 

 that the series of vertebrate animals now living, present 

 series of development which negative the sudden and 

 incomprehensible origination of these organs in an im- 

 mediate state of completion. How they appeared in 

 yet lower grades than are exhibited in the true fishes 

 of the present time we may learn in part from the 

 lancelet, and in part we may picture to ourselves from 

 the corresponding sensory apparatus of the lower Mol- 

 lusca, Articulata, and Annulosa. With reference to the 

 objections to his doctrine arising from the arrangements 

 of the most perfect organs, Darwin has said that he 

 would abandon his whole theory if it can be shown 

 that any of these organs could not possibly have been 

 formed from lower grades, by improvement slowly ac- 

 quired. This demonstration no one has yet undertaken, 

 nor will it ever be undertaken with success, as every 

 deeper penetration into the comparative anatomy of the 

 sensory apparatus affords evidence to the contrary. In 

 order to understand the presumptively faultless sensory 

 organs and their derivation from a lower grade, it is of 

 supreme importance to bear in mind the circumstance 

 first exhibited by Helmholtz in the eye, that besides a 

 number of perfections, they likewise possess a number 

 of imperfections, and purposeless or obstructive arrange- 

 ments. 



But we must examine another point, which may 

 awaken doubts as to the admissibility of the doctrine 

 of Descent, though, strangely enough, it has as yet been 

 turned to little account by adversaries, and only inci- 

 dentally touched upon by Darwin. In the " Origin of 

 Species," he states, that H. C. Watson, we know not 



